C函数来扫描和打印任何基本数据类型数组

Question

I want to make scan_array and print_array function that can scan and print any basic data type array from stdin to stdout.

What I got so far:

#include<stdio.h>
void scan_array(void* base, size_t size_of_one, size_t n, const char* fmt)
{
    char *element, *end;
    end = (char *)base + size_of_one * n; 
    for (element = (char *)base; element < end; element += size_of_one) {
        scanf(fmt, element);
    }
}

void print_array(void* base, size_t size_of_one, size_t n, const char* fmt) 
{
    char *element, *end;
    end = (char *)base + size_of_one * n; 
    for (element = (char *)base; element < end; element += size_of_one) {
        printf(fmt, *element);
    }
}
int main()
{
    double a[3];
    size_t n = 3;
    scan_array(a, sizeof(double), n, "%lf");

    int i;
    for(i=0; i<n;i++) {
        printf("%lf ", a[i]);
    }

    putchar('\n');

    // prints zeros
    print_array(a, sizeof(double), n, "%lf ");
    return 0;
}

scan_array function works for all basic types, I checked that with normal for loop inside main.

print_array function works for INTS but not for any of other basic data types.

First thought was to change print_array def so that it takes function pointer instead of const char* fmt like this

void print_array(void* base, size_t size_of_one, size_t n, void (*data_printer)(void *el))
{
    char *element, *end;
    end = (char *)base + size_of_one * n; 
    for (element = (char*)base; element < end; element += size_of_one) {
        data_printer(element);
    }
}

And than make double_printer:

void double_printer(void *el) 
{
    printf("%lf ", * (double *) el);
}

And it works perfectly.

print_array(a, sizeof(double), n, &double_printer);

But is there any way to make print_array without function pointer?

Answer 1

Actually, it has some bugs regards to int .

Try input 127 128 255 , it should return 127 -128 -1 .

The problem is char *element, *end; , and then dereference with *element , it only reads 8 bits, not whole 32 bits regards of double .

For this very case, I think define a macro is a better option, or you need to provide the function pointer as qsort in c does.